Continuous gas-atomized copper smelting and converting

ABSTRACT

A PROCESS FOR SMELTING COPPER SULFIDE CONCENTRATES AND SIMULTANEOUSLY CONVERTING THE THUS-PRODUCED MATTE TO FORM BLISTER COPPER, SLAG AND AN EFFLUENT GAS UNUSUALLY RICH IN SULFUR DIOXIDE IS CHARACTERIZED BY CONTINUOUS OPERATION IN WHICH BOTH SMELTING AND CONVERTING ARE CARRIED OUT IN   SUSPENSION OVER A COMMON FURNACE HEARTH BODY OF MOLTEN BLISTER COPPER, MATTE AND SLAG FROM WHICH THE MATTE TO BE CONVERTED IS SUPPLIED.

July 4, 1972 J. c. YANNOPOULOS 3,674,463

CONTINUQUS GAS-ATOMIZED COPPER SMELTING AND CONVERTING Filed Aug. 4,1970 5 Sheets-Sheet l Fluxes CQppe SuIfide Concenrrqte v Air/O2 FIG. 1

Pyrite A Furnace Gases V Shaft ,r-"I. T--,-..

Matte B|i$1'e|' Rec c|ed Copper y FIG. 2

Cooling I Water In Ii 1=Y E v L 1 Co n ce ntrclre 8 Flux Charge Gus JetsINVENTOR fj. John C. Yonnopoulos ."LQ'M av 28 15:? Z111K ATTORNEYS July4, 1972 CONTINUOUS GAS-ATOMIZED COPPER SMELTING AND CONVERTING FiledAug. 4, 1970 FIG. 3

J. c. YANNIOPOULOS 3,674,463

5 Sheets-Sheet Z I k R i l 0) N co N an N

2 i i "J 2-1- ID 01.! N O.\ \\\\Y.\\\\\\\ 0 0| 9 INVENTOR John C.Yonnopoulos y 1972 J. c. YANNOPOULOS 3,

CONTINUOUS GAS-ATOMIZED COPPER SMELTING AND CONVERTING 5 Sheets-Sheet 5Filed Aug. 4, 1970 Q h R INVENTOR John C. Yonnopoulos ATTORNEYS July 4,1972 J. c. YANNOPOULOS 3,674,463

CONTINUGUS GASATOMIZED COPPER SMELTING AND CONVERTING INVENTOR John C.Yonnopoulos a MM, 044. 77 Av EYS United States Patent 3,674,463CONTINUOUS GAS-ATOMIZED COPPER SMELTING AND CONVERTING John C.Yannopoulos, Danbury, Conn., assignor to Newmont Exploration Limited,Danbury, Conn. Filed Aug. 4, 1970, Ser. No. 60,793 Int. Cl. C22b 9/10,15/06 U.S. CI. 75-72 4 Claims ABSTRACT OF THE DISCLOSURE A process forsmelting copper sulfide concentrates and simultaneously converting thethus-produced matte to form blister copper, slag and an efiluent gasunusually rich in sulfur dioxide is characterized by continuousoperation in which both smelting and converting are carried out insuspension over a common furnace hearth body of molten blister copper,matte and slag from which the matte to be converted is supplied.

This invention relates to the smelting and converting of copper sulfideconcentrates and, more particularly, to a process for carrying out thesetwo operations simultaneously and continuously primarily in agas-atomized state.

Although the smelting and converting of copper sulfide concentrates havebeen satisfactorily performed for decades through the combination of thereverberatory furnace and PeirceSmith converter, the followingcharacteristics of the process have been considered unsatisfactory:

(l) Substantial fuel energy has to be provided to the reverberatoryfurnace, whereas the converter generates a significant amount of heatwhich cannot effectively be transferred to the reverberatory furnace;

(2) The intermittent recycling of slag rich in copper and in magnetitefrom the converter to the reverberatory furnace is known to cause highcopper loss in the slag and, hence, to decrease the overal copperrecovery;

(3) The batchwise movement of hot masses between the two separatefurnaces increases the process cost (large cranes, railway systems,ladies, ladle repair shops, heat losses, etc);

(4) The low rate of smelting per unit reverberatory furnace;

(5) The poor temperature control and heat distribution in thePeirce-Smith converter. Non-uniform heat distribution leads todestructive hot spots in the refractories near the tuyere line and tocold regions remote therefrom;

(6) The production of slag in the Peirce-Smith converter which is highin magnetite and copper content; and

(7) The dilute sulfur dioxide-containing reaction gas produced in thereverberatory and in the cyclic operation of the converter is tooexpensive to process for its sulfur content and thus creates a pollutionproblem in its disposal.

Smelting copper sulfide concentrates in suspension, a significantmodification in copper pyrometallurgy, has been in commercial operationduring the last two decades and has been characterized by highthroughput and high utilization of the heat generated during oxidationof the sulfides. This flash smelting, as it is called, produces coppermatte which has to be transported to a converter in order to beconverted to metallic copper. Although the flash smelting furnaceprocess requires less fuel than a reverberatory smelting process andpermits the production of sulfur dioxide in a more concentrated form,the copper content of the slag produced is high. Moreover, although theprocess in the flash smelting furnace is continuous, the matte producedis converted batchwise in a Peirce- Smith converter and therefore theoverall copper making operation cannot qualify as continuous. The flashsmelting process as presently operated cannot be adjusted to volume ofthe client converting, and thus produce metallic copper, by increasingthe amount of oxygen admitted with the concentrate because the resultingoxidized slag is extremely high in magnetite and tends to solidify. Itappears, therefore, that during flash smelting a matte and/or whitemetal phase is necessary to avoid a slag extremely high in copper andmagnetite and to accommodate the matte collected during any slagcleaning treatment.

I have now devised a method of controlling the suspension or flashsmelting of copper sulfide concentrates so that it can be combined withsuspension converting of the matte produced in a continuous operationwhereby the combined smelting and converting yields, as molten endproducts, a slag and blister copper and a gaseous product sufiicientlyhigh in sulfur dioxide to permit eflicient recovery of its sulfurcontent. The present invention is thus an improvement in a continuousprocess for smelting a copper sulfide concentrate wherein a stream of anintimate mixture of particulate copper sulfide concentrate and siliceousfluxing material is charged downwardly into a suspension smelting zoneand an oxidizing gas is charged at high velocity in a directionconverging downwardly and inwardly against the falling stream ofconcentrateflux mixture so as to disperse the stream into a particulatesmelting-promoting phase suspended in and carried downwardly in theoxidizing gas and thus form at the bottom of the vessel a molten body ofblister matte and a supernatant layer of molten slag. The improvement insuch a process, pursuant to the invention, comprises (a) introducinginto the lower portion of the falling particulate smeltingproducingphase a jet stream of reducing material at a rate sufficient to maintainthe partial pressure of oxygen below about l0 mm. of mercury in theatmosphere adjacent the surface of the slag layer, (b) charging into theupper portion of a converting zone a downwardly directed stream ofmolten copper matte, (c) charging an oxidizing gas at high velocity intothe downwardly moving stream of molten matte at a plurality ofperipherally located positions so as to disperse said stream into aparticulate converting-promoting phase, (d) directing the descendingparticulate converting-promoting phase through the aforesaid atmosphereadjacent the supernatant slag layer, (e) collecting below the fallingstreams of smelted and converted materials a common body of the moltenresulting products of the aforementioned smelting and converting in theform of a bottom layer of blister copper, an intermediate layer ofcopper matte and a supernatant layer of slag, and (f) returning thethus-formed molten copper matte to the top of the converting zone as thesource of matte charged thereto. In the presently preferred embodimentof the invention, the smelting and converting zones are combined in asingle zone, but they can be carried out separately above and in directcommunication with a common body of the molten products therebeneath.

These and other novel features of the process of the invention will bemore readily understood from the following description taken inconjunction with the accompanying drawings in which FIG. 1 is aschematic drawing of the process in which both smelting and convertingare carried out in a common zone;

FIG, 2 is a cross-sectional detail view of the upper charging end of theapparatus shown in FIG. 1;

FlG. 3 is a side elevation of the furnace used in the process shownschematically in FIG. I;

FIG. 4 is a plan view of the furnace hearth taken along line 44 in FIG.3;

FIG. 5 is a crosssectional view of the furnace hearth taken in thedirection of the arrows 5 along line AA in FIG. 4;

FIG. 6 is a cross-sectional view of the furnace hearth 3 taken in thedirection of the arrows 6 along the line A-A in FIG. 4',

FIG. 7 is a detailed material flow balance imposed on the schematicdrawing of FIG. 1 pursuant to a specific example of operation of theprocess;

FIG. 8 is a schematic drawing of a modification of the process of theinvention in which the smelting and converting zones are separate; and

FIG. 9 is a schematic drawing of another modification of the process inwhich the smelting and converting zones are separate.

In the process represented in FIG. 1, incorporating atomized dispersedconverting and suspension smelting in a common zone, the ratio of oxygento copper sulfide concentrate is adjusted to transform from 35 to 75% ofthe copper into blister copper and the rest into high grade matte. Allof the silica required for a good slag is added with the concentrate atthe top of the furnace shaft. The proportion of the silica charged, andthe operating temperature, can be higher than in the Peirce-Smithconverter inasmuch as the reactions are taking place in suspension andnot in contact with the refractory walls. A fraction of the coppersulfide concentrate is also added near the bottom of the shaft as atemperature control and safeguard against a high partial pressure ofoxygen which would otherwise cause magnetite formation. Copper and highgrade matte are continuously tapped at one end of the furnace hearth,and slag is skimmed at the other end. The matte is recycled into theprocess, at the rate that it is produced, and is sprayed pneumaticallydown wardly into the top of the shaft. This recycled matte is convertedexothermically to blister copper by the appropriate air flow.

In order to effect mixing of the copper sulfide concentrate with thefluxes and with the matte for the forma tion of the workable slag, athin column of the incoming matte is encircled, as shown in FIG. 2, witha cylindrical ring charge of well mixed fine concentrate and fine fluxeswhich, in turn, are splashed, atomized and dispersed by a number ofpowerful jets of air or oxygen-enriched air. The violent action of theatomizing nozzles at the top of the shaft produces an intimate mixtureof the reactants in the form of a co-current gravitational flow of agasliquid suspension of the concentrate fiux-matte mixture movingdownwardly through the shaft. Inasmuch a the converting-and slag-formingreactions take place a distance inwardly from the refractory walls, theproportion of the flux charged per unit of concentrate and the operatingtemperature of the mixture can be higher than in the conventionalPeirce-Smith converter.

As pointed out hereinbefore, an appropriate fraction of the fine dryconcentrate is blown with Garr guns or the like through four auxiliaryentrances near the bottom of the shaft and using recycled flue gas orany conventional reducing gas as the carrier (FIG. 1). The resultingdispersion of fine concentrate among the falling droplets serves as areducing agent to control the oxygen partial pressure of the gases inthis portion of the smclt ing and converting none to an extremely lowlevel and at the same time controls the temperature and formation ofmagnetite. This low oxygen partial pressure at the bottom of the shaftin the atmosphere adjacent the surface of the supernatant slag layer.generally below 10 and preferably below 10- min. of mercury. is anindispensable condition in the practice of the invention and can beachieved by one or more of the following expendients:

(a) Blow-in copper sulfide concentrates with hot inert stack gas:

(b) Mix coal fines with the concentrate or introduce reducing flameswith the concentrates: or

(c) Move upwardly the auxiliary concentrate flash entrances (in otherwords, decrease the ratio of the respective heights h':h" in FlG. 1).

Control of the temperature and magnetite formation in the lower portionof the furnace shaft is effected by the secondary smelting of theconcentrate charged at this point which consumes part of the heatproduced in the shaft by the converting reaction and thus cools theliquidgas interface at the furnace hearth to the appropriatetemperature. This cooling can be regulated by preheating (or not) theconcentrate and by controlling the temperature of the carrier gas of thesecondary smelting operation so that the temperature of the supernatantslag immediately below the shaft will permit the dissolving of anymagnetite formed and not previously reduced as the reactants movedownwardly through the low-oxygen atmosphere immediately above thesurface of the slag layer. In this way, there is always an excess ofnon-reacted sulfur and iron (the iron being an indigenous constituent ofthe copper sulfide concentrate) at the bottom of the smelting shaft. Theiron sulfide reduces any mag netite according to the reaction:

Thus, the partial pressure of oxygen at the bottom of the shaft can bealways controlled to an extremely low level in spite of inadvertentrandom feed variations.

A cleaning treatment of the slag is advantageously provided throughsmelting of pyrite or pyrrhotite introduced by Garr gun blowers, or thelike, into the low-oxygen containing atmosphere immediately above thesurface of the slag layer in the furnace hearth. This, along with thecountercurrent flow of slag versus matte in the settler as the result ofseparate withdrawal of the slag and matte from opposite ends of thefurnace hearth, reduces copper losses and magnetite content in the slag.A copper concentrator middling product, low in copper and high in sulfurand iron, can be used in lieu of the pyrite or pyrrhotite for theoverall economy of the copper extraction process.

The general configuration of the furnace for carrying out the foregoingprocedure is shown in FIG. 3 with its accompanying liquid. The primarysmelting zone 10 and the converting zone 11 are located within thefurnace shaft 12, and the concentrate-flux mixture is supplied through asolid feeder 13 which air is supplied through nozzle 14 at the top wallof the shaft 12 in an arrangement such as that shown in FIG. 2. At thebottom of the shaft 12 there are openings 15 provided for supplying theauxiliary concentrate for smelting in the secondary smelting none 10a. Aconventional tap 16 for blister copper 17 is provided at the bottom ofthe furnace hearth l8, and another conventional matte tap 19 is providedat the deep end of the hearth for drawing off the matte 20. The matte iscollected in a recycling ladle 21 which is capable of being raised by acable 22 to its upper dotted position where the ladle is tilted to pourits contents into a tundish 23 at the top of the furnace shaft 12.Pyrite, or pyrrhotite, for cleaning the slag is introduced throughobliquely arranged openings 24 in the roof 25 of the furnace hearth. Thesupernatant slag layer 26 is drawn off through a conventional slag taphole 27 located at the end of the furnacc hearth opposite the matte tap19. The process gas ellluent is collected in an uptake section 28 and isremoved through a flue 29.

As shown in FIGS. 4, 5 and 6, the furnace hearth is provided withdifferent cross-sectional shapes under the smelting-converting zone andunder the settling zone represented, respectively, by the arrows 55 and66 at the transverse hearth line AA in FIG. 4. The hearth shape underthe smelting-converting zone is shown in FIG. 5 and is substantiallytrough-shaped so that the interfaces between the hearth atmosphere andslag, the slag and the matte, and the matte and the blister copperprogressively decrease in area. The hearth shape in the settler zone,shown in FIG. 6, is substantially rectangular.

Blister copper, matte of different grades up to white metal, slag,unreacted solids, and a gas phase with extremely low oxygenconcentration, enter the settler system defined by the furnace hearth 18at the bottom of the shaft. As these products, falling through the shaftand still continuously reacting, hit the surface of the liquid slag 26in the molten bath, a sharp deceleration occurs which causes coagulationof similar phases and sinking of the heavier liquids. Three liquidphases (blister copper 17, matte 20 and slag 26) thus form and settle asthree distinct layers. The concentrations of copper, sulfur, iron andoxygen in the matte are far from being uniform throughout the mattelayer due to their dilferent origins in the shaft reaction zone and inthe different reaction times of the individual droplets. Diffusionphenomena continue into the phases and among them. Due to specificgravity differences and to the continuing actions at the lower and upperinterfaces of the intermediate matte layer, high grade matte (whitemetal) accumulates in contact with the bottom blister copper layer andmatte poorer in copper sulfides accumulates immediately below thesupernatant slag layer. The trough shape of the furnace hearth below thesmelting-converting shaft makes the interphase surfaces area diminishingin the order of gas-slag, slag-matte and white metal-blister copper andthus slow down the tendency for reversal of the converting reaction totake place in the furnace hearth.

Matte is continuously tapped into the ladle which is vertically movedinto the heated tundish whereby the matte is continuously recycled tothe top of the shaft at the rate that it is produced. The main controlon the matte production is the rate of secondary smelting of concentrateintroduced through the auxiliary supply openings near the lower portionof the shaft. The optimum depth of the matte layer is advantageouslycontrolled by continuously monitoring the density of the molten phasesin the furnace with conventional gamma-ray density gages.

The following specific example of a material and heat balance isillustrative but not limitative of the continuous production of blistercopper from chalcopyrite concentrate pursuant to the invention.Chalcopyrite concentrate of the following composition is the chargedcopper sulfide concentrate:

Percent:

C'uFeS z 83. 76 FeS: 7. 54

NoTu.Molstn1-e: 1% (dry basis).

The flux materials admixed with the copper concentrate are made up ofquartzite of the following composition:

Percent SiO 98.8 Fe 0.2 MgO 0.2 A1 0 0.4

Moisture: 1% (dry basis).

and pulverized limestone with the following composition:

Percent Si0 4.0 A1 0 3.3 MgO 2.7 CaCO 89.0

The pyrite concentrate for the auxiliary flash operation to controlcopper losses in the slag has the following composition:

Percent:

NOTE.Molsture: 1% (dry basis).

With a furnace shaft inner diameter of 18 feet, copper concentratecharged at the rate of 1,080 tons per day, and air charged at the rateof 34,000 standard cubic feet per minute, the average linear velocity ofthe gas downwardly through the shaft is about 11 feet per minute at anaverage temperature of 1200 C.

The matte which is formed and recycled to the top of the furnace shaftcontains 75% Cu, 20.9% S, 3.8% Fe and 0.25% 0 and 70% of the copper inthe concentrate charged is converted to blister in the first pass.

The complete material balance per ton of concentrate fed is given inFIG. 7. Overall copper recovery is 98.9% and the slag and eflluent gascompositions are:

Slag: Percent Cu 0.29

FeO 43.8

Ffiao 8.0 S 1.1 FeS 0.2 SiO, 35.0 CaO 4.6 A1 0 2.5 MgO 1.0

Gas:

-, 16.9 N; 81.1 52 2 Had I::IIIIIIII::::::::: 1I1

The process is autogenous except for a minor quantity of fuel (12.7standard cubic feet of natural gas/ton of copper concentrate) which isburned for the auxiliary pyrite smelting.

The process of the invention thus consists in effect of two systemsrepresented by the numerals I and II in FIG. I:

System I, where smelting and partial converting is taking place: This isa system in suspension with extremely fast process rates. Stronglyoxidizing conditions prevail at the top of this system and areattenuated towards its bottom. Excess silica and high temperature existalong this system, and the reacting species stay for an extremely shorttime (0.054. sec.) in it.

System II, where smelting and dc-converting" (the opposite to convertingreactions) are taking place: With the intimate mixing of someconcentrate flashed towards the falling products of System I, the oxygenactivity drops to an extremely low level (P l0- mm. of mercury) and anymagnetite formed is reduced according to the reaction:

In comparison with System I, the lower phases in System II (blistercopper and matte) are quiescent and almost stagnant with an interface ofrestricted area. With the proper atomization in System I, the interphasearea among the reacting phases is much larger than in System II.Therefore the rate q" (lb. cu/min.) at which blister copper is"de-converted" in System II is substantially smaller than the rate q(lb. cu/rnin.) at which blister copper is produced in System I. Thedifference between q and q" constitutes the production capacity of theprocess, and its magnitude depends on the degree of atomization in theshaft furnace, the oxygen content of the atomizing gas and the furnacesize. Although all of the oxidizing gas is added through the top of theshaft, System I opcrates with a substantially stoichiometric oxygendeficiency due to the continuous recycling of the matte. This oxygendeficiency, along with the excess of silica flux, the high convertingtemperature and the very short residence time in the shaft, prevent theundesirable oxidation of iron to magnetite. In the furnace hearth, onthe other hand, the extremely low oxygen partial pressure, thehorizontal counter-current flow of slag and matte, the long residencetime and the pyritic cleaning, produce a slag very low in copper.

Two modifications of the process of the invention are shown in FIGS. 8and 9. In FIG. 8, an auxiliary furnace shaft is provided forgas-atomized converting of the recycled matte to blister copper. Thesmelting of the copper sulfide concentrate in suspension takes place inthe main shaft in which no matte is recycled, and a minor fraction ofthe concentrate is blown through Garr guns at the bottom of this shaftas in the operation shown in FIG. 1. The recycled matte issuspension-converted in an adjacent shaft, and both shafts are in directcommunication at their lower ends directly above the furnace hearth. InFIG. 9, the suspension-smelting of the copper sulfide concentrate iseffected obliquely in a direction such that, as in FIG. 8, the dischargeends of the converting and smelting suspension zones are in directcommunication above the furnace hearth. In both these alternativemodifications, a distinct step of matte-converting in suspension iscombined with a suspension-smelting step in a manner such that a verylow partial pressure of oxygen prevails at the point where the productsof the two-steps emerge and fall into the common molten phases in thesingle furnace hearth.

It will be seen, accordingly, that the process of the present inventionis characterized by the following advantages:

(1) Process continuity in a single furnace and thus lower labor andmaintenance cost;

(2) Excellent utilization of the converting reaction heat with theresult that the process is substantially autogenous;

(3) Extremely short residence time in the oxidation zone controlsmagnetite formation and minifies copper losses;

(4) The process operates with an artificial oxygen deficiency imposedand controlled primarily by matte recycling. This oxygen deficiency andthe control nonoxidizing gas phase immediately above the settler alsodiscourage magnetite formation and decrease copper losses;

(5) Both smelting and converting take place primarily in suspension outof contact with the walls of the reaction, and thus refractory wear isless than in other processes;

(6) Excess silica can be used during the converting step with resultingimprovement in overall copper recovery;

(7) The process does not use tuyeres and/or lances which, in prior areprocesses, have been extremely sensitive to high temperature wear andcorrosion;

(8) The countercurrent movement of matte and slag in the molten body inthe furnace hearth, along with the cleaning treatment of the highlyfluid siliceous slag, reduces the copper loss to a lower level thanduring conventional smelting;

(9) The systems in suspension have high mass and heat transfercoefficients due to their inherently high interphase areas. A high rateof smelting per unit volume of furnace is thus obtained;

(10) The continuous nature of the process makes it adaptable toautomated process control; and

(11) The process efiluent gas is produced continuously and with a highsulfur dioxide content readily amenable to efiicient recovery of itssulfur content.

I claim:

1. In a continuous process for smelting a copper sulfide concentrate toproduce matte and slag in the form of superimposed molten phases whereina stream of an intimate mixture of particulate copper sulfideconcentrate and particulate siliceous fluxing material is chargeddownwardly into a suspension smelting zone and an oxidizing gas ischarged at high velocity in a direction converging downwardly andinwardly against the falling stream of concentrate-flux mixture so as todisperse the stream into a particulate smelting-promoting phasesuspended in and carried downwardly in the oxidizing gas and thus format the bottom of the vessel a molten body of matte and a supernatantlayer of molten slag, the improvement which comprises (at) introducinginto the lower portion of the falling particulate smelting-promotingphase a jet stream of reducing material at a rate suflicient to maintainthe partial pressure of oxygen below about 10- mm. of mercury in theatmosphere adjacent the surface of the slag layer, (b) charging into theupper portion of a converting zone a downwardly directed stream ofmolten copper matte, (c) charging an oxidizing gas at high velocity intothe downwardly moving stream of molten matte at a plurality ofperipherally located positions so as to disperse said stream into aparticulate converting-promoting phase, (d) directing the descendingparticulate converting-promoting phase through the aforesaid atmosphereadjacent the supernatant slag layer, (e) collecting below the fallingstreams of smelted and converted materials a common body of the moltenresulting products of the aforementioned smelting and converting in theform of a bottom layer of blister copper, an intermediate layer ofcopper matte and a supernatant layer of slag, and (f returning thethus-formed molten copper matte to the top of the converting zone as thesource of matte charged thereto.

2. The process according to claim 1 in which the smelting and convertingare carried out in a common zone by introducing the molten matte in astream directed downwardly through the center of said common zone,charging the concentrate-flux mixture peripherally around and into thestream of molten matte, and directing the converging streams ofoxidizing gas into the admixed streams of molten matte andconcentrate-flux mixture to form therebelow said common molten body ofblister copper, matte and slag.

3. The process according to claim 1 in which the suspension-smelting andsuspension-converting are carried out in separate zones the lower endsof which both communicate with the low-oxygen atmosphere adjacent thesurface of the supernatant slag layer in a furnace hearth common to thetwo suspension zones.

4. The process according to claim 1 in which the copper sulfideconcentrate suspension is charged obliquely above the hearth of thefurnace in a direction such that the discharge ends of the convertingand smelting suspension zones are in direct communication in the lowoxygen atmosphere adjacent the surface of the supernatant slag layer inthe furnace hearth.

References Cited UNITED STATES PATENTS 3,459,415 8/1969 Holeczy 7572 XFOREIGN PATENTS 890,282 2/1962 Great Britain 7560 L. DEWAYNE RUTLEDGE,Primary Examiner J. E. LEGRU, Assistant Examiner US. Cl. X.R. 75-74

